1. Field of the Invention
The present invention relates to medical devices containing a needle cannula such as syringes, evacuated tube holders and the like. More particularly, the present invention relates to safety needle devices having self-contained safety shields which can be positioned to help prevent accidental contact with the needle point.
2. Description of Related Information
Generally speaking, a hypodermic syringe includes a cylindrical barrel, commonly made of thermoplastic material or glass, having a distal end connected to a sharpened needle cannula and a proximal end adapted to receive a stopper and plunger assembly.
In recent years there has developed an increased concern regarding the transfer of disease, infection or the like to syringe users and health-care professionals who accidentally stick themselves with hypodermic needles while disposing of used hypodermic syringe products. In many areas in a hospital, where needle cannula products are used, disposal bins are provided so that a syringe or other needle cannula product may be immediately discarded in a safe rigid container. However, there are areas of medical practice such as in emergency rooms, or other areas where disposal containers are not readily available or practical, where products having self-contained shielding devices are desirable. In theory, after the syringe is used to inject medication or for another purpose, a shield which surrounds the syringe barrel is advanced to an extended position and locked to prevent further contact with the sharp needle tip. The syringe, in this condition, can be safely transported to a disposal system.
Such a syringe is taught in U.S. Pat. No. 4,631,057 to Mitchell. This syringe contains a needle guard which is releasably retained in a retracted position, for allowing the syringe to be used for injection, and lockably retained in the extended position. To lock the needle guard in the extended position the user moves the needle guard axially distally along the syringe barrel until it snaps in the locked position. No further manipulation of the needle guard, such as rotation, is required.
A similar syringe is taught in U.S. Pat. No. 4,747,837 to Hauck. This patent teaches a syringe having a cylindrical sheath sleeve which can be advanced axially to a locked irreversible position which prevents further access to the needle cannula tip.
Other shielded syringe designs such as the syringe as taught in U.S. Pat. No. 4,998,920 to Johnson, U.S. Pat. No. 4,801,295 to Spencer and U.S. Pat. No. 5,053,018 to Talonn et al. allow the needle guard to be moved to a substantially fully extended position, through axial movement, without locking the needle guard. In this position, the syringe assembly appears to be safe, however, the needle guard can still be moved in a proximal direction to expose the sharp needle tip. These designs require an additional rotation of the needle guard, while the needle guard is fully extended, to place it in a locked position where it will not move proximally to expose the needle.
It can be seen, especially with designs requiring additional rotational movement of the needle guard to lock the needle guard in the extended position, that the syringe and needle guard assembly may appear to be safe to the user but the user can not be sure of its locked condition without carefully experimenting with the syringe assembly to determine its status.
Other safety needle devices such as evacuated blood collection tube holders are being designed to overcome the same problems that syringes face with respect to shielding and disposal. U.S. Pat. No. 4,871,355 to Kikkawa teaches an injury resistant needle and blood collection tube holder having an outer protective tube which is movable axially between the position where the needle protrudes for venipuncture to a position wherein the needle is housed entirely within the new protective tube.
A similar blood sampling device with shield is taught in U.S. Pat. No. 4,840,185 to Hernandez wherein a protective shield moves over helical grooves to permit longitudinal movement of the shield into positions which expose the needle for venipuncture or to enclose the needle and protect the user from accidental needle sticks.
Although the prior art teaches products which enhance the safety of needle device users by allowing the needle to be safely covered by a needle guard after use, there still exists a need for a simple, straight forward, reliable, easily fabricated safety needle device which provides the user with clear visual indication that the needle guard is in a locked safe position or that, even though the needle is covered by the needle guard, the needle guard is not in a locked safe position.